Lianas, vines or rarely shrubs, frequently becoming canopy lianas. Leaves opposite or subopposite, rarely alternate, simple, entire, petiolate, membrana-ceous or coriaceous, with glands at the base of the blade or at the apex of the petiole; stipules small and caducous or absent. Inflorescences of umbelliform corymbs, umbels or pseudo-umbels, arranged in dichotomous cymes. Flowers pedicellate with pedunculate pedicels, the central cluster of flowers frequently sessile, the lateral clusters pedunculate; bracts and bracteoles conspicuous; sepals 5, membranaceous or thick, ovate or oblong, with 4 pairs of glands; petals un-guiculate, yellow, sometimes marked with orange or red at the center, the limb orbicular or elliptic, often more or less concave, the margin denticulate or fim-briate, the interior petal often smaller; stamens 10, unequal, the filaments gla-brous, flattened, united briefly at the base, the anthers unequal, the 4 opposite the lateral sepals generally reduced and practically sterile, the remaining 6 well developed, the 3 opposite the pistil larger; ovary trilocular, trilobate, the styles 3, free, erect or curved, somewhat flattened, dilated at apex, spathulate-truncate with the inner angle obtuse and stigmatic, the outer angle acute or apiculate in the medial style, the medial style bilaterally, and symmetrically winged or ap-pendiculate, in the lateral styles unilaterally winged, the appendages foliaceous and pendulous or only enlarged horizontally into a pediform projection. Fruit a schizocarp of three samaras, the seminiferous area rounded or ovoid, smooth, verrucose, tuberculate or with crestlike appendages; the dorsal wing membran-aceous or subcoriaceous with the ventral margin thickened and smooth, the dorsal margin thin, frequently crenulate; rarely with the wing reduced to a crest (section Brachypterys).
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